Various devices for producing an optical lens made from this kind of material are already known in the art that include a closure member adapted to grip two molding shells circumferentially to define a molding cavity in conjunction with said shells. In some devices, the closure member is an adhesive tape applied to the edges of the two molding shells. In other devices it is an annular elastomer seal.
International application WO 93/21010 describes a device in which the closure member is a flexible annular seal fitted around one of the molding shells with a rigid clamp fixed around the flexible seal to reinforce it. The second molding shell is then inserted in the flexible seal by a carriage which positions it at the required distance from the first shell, the carriage then being locked in position. A source of molding material is connected to the molding cavity by a flexible conduit having a frustoconical end engaged in a small hole formed in the lower portion of the seal.
International application WO 03/078144 also describes a device in which the closure member is a flexible annular seal incorporating a hole for filling the molding cavity, this hole being formed in the upper portion of the seal and receiving a nozzle for introducing the molding material, to be more precise an assembly comprising the nozzle for introducing the polymerizable material and another nozzle that is used at the end of filling to aspirate surplus polymerizable material.
There is also known from European patent EP 0 715 946, and from its counterpart U.S. Pat. No. 5,547,618, a device described hereinafter with reference to FIGS. 1 to 3 of the appended drawings, in which:
FIG. 1 is a perspective view of the device;
FIGS. 2A, 2B, 2C and 2D are views to a smaller scale similar to that of FIG. 1 showing successive operations of using the device; and
FIG. 3 is a perspective view to the same scale as FIG. 1 showing the removal from the mold of the optical lens produced by the device.
The lens 10 shown in FIG. 3 is produced by the device 11. It is a blank for eyeglass lenses, for example, and would subsequently have its periphery trimmed to the required shape for fitting it into an eyeglass frame.
Here the general contour of the lens or blank 10 is circular.
The device 11 includes two jaws 12′ and 12″ which are adapted to grip conjointly between them the edges of two molding shells 14A and 14B disposed substantially parallel to each other, to constitute a mold 13, forming with respect to these molding shells 14A and 14B a closure member 12 defining with them the required molding cavity 15.
Here the jaw 12′ is fixed and the jaw 12″ is mobile.
The molding shells 14A and 14B have internal surfaces (which face each other when the mold is assembled) whose geometry corresponds to that required for the lens to be produced.
Let EA and EB be the thicknesses of the molding shells 14A and 14B along their edge 16 and let EC be the distance between them required to constitute the molding cavity 15.
The interior surface 18 of each of the jaws 12′ and 12″ is generally semicylindrical, following the radius of the peripheral contour of the molding shells 14A and 14B.
The jaws 12′ and 12″ are interengaged with a common frame 19, formed here by two lateral flanges 20 and a crossmember 21 connecting the lateral flanges 20 together at one of their ends. The lateral flanges 20 extend vertically and parallel to each other, and the crossmember 21 extends horizontally at their upper end.
The two jaws 12′ and 12″ are staggered vertically on the frame 19, along the lateral flanges 20, the axis of their interior surfaces 18 therefore being horizontal.
The mold that the jaws 12′ and 12″ form with the shells 14A and 14B therefore also has a horizontal axis.
The jaw 12′ is fixed to the frame 19, here screwed to it, and the jaw 12″ is slidably interengaged with grooves 22 provided for this purpose on the frame 19, to be more precise on the internal face of the lateral flanges 20.
Each of the jaws 12′ and 12″ is formed by a solid metal block.
The interior surface 18 of each of the jaws 12′ and 12″ has a synthetic material covering 23 that is fixed by means of a semicircular clamp 24 provided at each of the curved ends of the surfaces 18.
The distance D between the two clamps 24 is greater than the sum of the thicknesses EA and EB of the molding shells 14A and 14B and the distance EC between them.
The lower jaw 12′ has a bore 25 passing completely through it, forming a casting opening 26 for the molding cavity 15 where it opens onto its interior surface 18. The upper jaw 12″ also has a bore 28 passing completely through it and forming a vent.
Here, the casting opening 26 is at the lowest point on the interior surface 18 of the lower jaw 12′ and the bore 28 in the upper jaw 12″ opens onto the interior surface 18 of that jaw at its highest point.
The jaw 12″ is driven by two double-acting cylinders 29 disposed parallel to each other.
The body 30 of each cylinder 29 is carried by the crossmember 21 of the frame 19 and its piston rod 31 is coupled to the mobile jaw 12″.
The bore 25 in the fixed jaw 12′ is connected to a pipe 32 for connecting the molding cavity 15 to any kind of supply of molding material (not shown).
The use of the device 11 is described next.
Initially, the mold 13 is assembled.
To this end, the upper jaw 12″ is moved away from the lower jaw 12′, the molding shells 14A and 14B are fitted to the lower jaw 12′ by simply nesting them in the interior surface 18 of that jaw, on edge, spaced from each other and parallel to each other, the distance EC between them corresponding to that required for the molding cavity 15 to be formed (FIG. 2A).
Merely nesting the molding shells 14A and 14B in the interior surface 18 of the jaw 12′ is sufficient to retain them.
The double-acting cylinders 29 then lower the jaw 12″ until its interior surface 18 presses on the edge of the molding shells 14A and 14B (FIG. 2B).
With the mold 13 closed in this way, it can be filled via the pipe 32, the necessary quantity of molding material being introduced into it by pumping means adapted to ensure a continuous feed, i.e. a smooth feed, of molding material to the molding cavity 15.
Polymerization of the material placed in the mold in this way is then initialized by exposing it to light.
To this end the device 11 is associated with a source 33 of radiation that is offered up in line with one of the molding shells 14A and 14B, here the shell 14A (FIG. 2C).
Here the radiation source 33 is a source of ultraviolet radiation and the molding shell 14A is of glass at least partially transparent to ultraviolet radiation.
When at least initial polymerization of the optical lens 10 to be obtained has been effected, the mold 13 is opened by raising the upper jaw 12″ by means of the double-acting cylinders 29, after which the block 34 consisting of the optical lens 10 and the shells 14A and 14B gripping the lens 10 is removed from the lower jaw 12′ (FIG. 2D).
After completion of polymerization of the molded material, if necessary, the molding shells 14A and 14B are removed from the optical lens 10 (FIG. 3).
There are known from European patent applications 1 440 780 and 1 440 788 and from corresponding US patent applications 2004/0150125 and 2004/0262792, respectively, a device similar to the device 11 that has just been described but which includes, for connecting the molding cavity 15 to the supply of molding material, instead of a simple bore 25 to which the pipe 32 is directly connected, a filler device including a valve and a nozzle: the valve is mounted underneath the jaw such as 12′ and the nozzle is disposed in the jaw, the valve having a flow passage for the molding material whose inlet orifice communicates with the pipe such as 32 and whose outlet orifice communicates with the nozzle, which has an interior passage having the same function as the bore 25.
There is finally known in the art a machine conforming to European patent applications EP 1 440 780 and EP 1 440 788 just referred to in which the assembly of the nozzle and the covering such as 23 of the jaw such as 12′ is effected by adhesive bonding, the covering such as 23 being cut to form a casting opening such as 26 in line with the interior passage of the nozzle.